The term “ethylene-propylene-diene polymer,” (or “EPDM”) as used herein, is a saturated interpolymer chain composed of units derived from ethylene, propylene, and a diene. EPDM has a wide range of applications, such as insulation for wire and cable, hoses, and molded articles, for example.
Semi-crystalline EPDM grades (EPDM with at least 60 wt % units derived from ethylene) exhibit melt fracture during pelletization. The resulting melt fracture creates a rough surface with crevices trapping water during underwater pelletization, thereby making it difficult to dry the EPDM pellets in the process. Conventional dryers are unable to dry the pellets since the drying kinetics is diffusion rate controlled. The residual moisture results in long and costly warehouse drying times (on the order of weeks to months) before the EPDM pellets are sufficiently dry or can be shipped to customers for use.
Over time, the residual moisture migrates from the EPDM pellets and condenses on to the inner wall of the storage bags, or on to the inner surface of stretch-wrap covering the pallets supporting bulk pellets. This moisture condensation creates a quality concern for customers and end-use.
Conventional anti-blocking coatings such as talc and polyethylene dust, fail to mitigage moisture condensation within the packaging. A need exists for a process and system for packaging EPDM pellets, particularly semi-crystalline EPDM pellets, which reduce moisture condensation within the storage package.